Ammonia production and its contribution to urinary nitrogenous compounds in chickens fed low or high protein diet

The rates of total ammonia production and of ammonia retention and contribution of endogenous ammonia to urinary nitrogenous compounds were assessed using a constant intravenous infusion method with [15N]ammonia for 6 h in adult cockerels fed 7.00 or 1.75 g of protein per kilogram body weight per day for 5 d. At the 7.00-g protein intake level the mean total body ammonia production rate was 47.1 mumol/kg per min, with total excretion and retention rates being 10.1 mumol/kg per min and 37.0 mumol/kg per min, respectively. In birds with 1.75 g protein intake the mean total body ammonia production rate was 27.9 mumol/kg per min, with total excretion and retention rates being 3.1 mumol/kg per min and 24.8 mumol/kg per min, respectively. These values were significantly different between the two dietary groups (P less than 0.05-0.01). Ammonia N produced at low and high levels of dietary protein intake, contributed 33% and 84% of urinary uric acid N and 27% and 58% of urinary total N, respectively. With the above protein intake levels, 88% of urinary ammonia N and 6-9% of urinary nitrogenous compounds other than ammonia and uric acid were donated by ammonia N produced in the body. It is concluded that ammonia N produced in the body is the main source of uric acid N, which entirely explains the increase in urinary total N caused by feeding a high protein diet.